WASHINGTON, DC—Conditions related to allergy are responsible for billions of dollars in health care expenditures annually. Adding to this already high figure, a recent study found that the costs for treating seven other conditions—asthma, anxiety disorder, depression, migraine, otitis media, sinusitis, and tonsillitis—increase significantly during allergy season, even in patients who do not suffer from seasonal allergic rhinitis.[1]

Researchers from the MEDSTAT Group (a health information company) conducted a retrospective cross-sectional analysis of medical claims data from 1995 and 1996. People with allergic rhinitis or any of the other conditions listed in the previous paragraph were identified, and incidence rates were calculated separately for allergy and nonallergy seasons. Severity of illness was extrapolated from data on the amount spent in health care payments, as it was assumed that greater disease severity corresponded to greater expenses. Seasonal drug expenditures were also calculated. Weekly outdoor allergen levels were obtained from national surveillance data, and only patients who lived within 15 miles of an allergen counting station were eligible for inclusion.

HIGH LEVEL OF COMORBIDITY

The analysis included 40,188 people with at least one of the conditions of interest. The incidence of all conditions was significantly higher during allergy season than during nonallergy seasons, sometimes twice as high. This finding applied not only to disorders with a known link to allergens, such as rhinitis and allergy, but also to migraine, depression, and anxiety.

For each condition, spending was higher during allergy season than at other times. Using regression analysis to adjust for the presence of allergic rhinitis, the investigators compared predicted expenditures during allergy season with those during nonallergy seasons. In each case, expenditures during allergy season were significantly higher than they were in nonallergy seasons; the increases in spending ranged from 3.7% for asthma to 29.2% for anxiety. Thus, it appears that allergen levels may affect other conditions even in the absence of allergic rhinitis.

Existing literature has reported that patients with sinusitis who also have allergic rhinitis experience a worsening of symptoms during allergy season. Additionally, allergic rhinitis has been associated with higher rates of depression and anxiety and increased mental-health–related expenditures. Allergic rhinitis is also common in people who suffer from migraine headaches.

The investigators hypothesize that when allergic rhinitis coexists with any of the conditions studied, it acts as an aggravating factor. “If that is true,” they state, “the severity of allergic rhinitis will parallel that of the other illnesses. … [T]his will hold regardless of the reason for the coexistence of allergic rhinitis and the [other] conditions.”

To test this will require a study with a large and medically diverse population that will continue through many seasons. The authors admit that performing such comprehensive studies using longitudinal databases would be costly and time consuming, but they add, “the high and growing prevalence of allergy-related illnesses suggest[s] that the investment would be wise.”

—Gale Jurasek